Functional fluid compositions



United States Patent ()fiice 3,173,873 FUNCTIONAL FLUID COMPOSITIONS Kenneth L. McHugh, Kirlrwood, M0., and John 0. Smith, Swampscott, Mass assignors to Monsanto Research Corporation, St. Louis, Mo, a corporation of Delaware No Drawing. Filed Jan. 23, 1962, Ser. No. 168,245 5 Claims. (Cl. 252-75) This invention relates to liquid fluids of high thermal stability and more particularly provides functional fluids comprising polyphenyl ethers and certain organometallic compounds as adjuvants therefor.

The polyphenyl ethers are known compounds which have found wide application as functional fluids owing to their very good thermal stability, lubricity, and resistance to foam. For example, they have been found to be valuable as hydraulic fluids, as heat-exchange media, as atomic reactor coolants, as diffusion pump fluids, as lubricants in motor operation generally, and particularly as jet engine lubricants.

With recent changes in the design of aircraft engines, there is a demand for lubricants which will perform satisfactorily under conditions far more rigorous than ever contemplated in the past. A particularly important requirement for lubricants intended for use in the newly designed engines is that their viscosity be unaffected by the high temperatures to which they are necessarily subjected.

As is known in the art, petroleum lubricants generally comprise, in addition to the petroleum base stock, additives or adjuvants which impart specifically desired properties to the base stock, e.g., rustinhi-bitors, antioxidants, extreme pressure-resisting agents, lubricity improvers, deter-sives, etc. The additives proposed heretofore have been designed to accommodate the requirements of petroleum base stocks for lubrication in conventional equipment such as internal combustion engines of the automotive type, diesel engines and the like. One feature in common with respect to these various applications was that the temperature of use was not excessive, i.e., it may vary from about 40 F. to 400 F. With the advent of extremely high speed aircraft of the jet type, it was found that neither the petroleum base stock nor the conventional additives used therewith were practical, because the lubricant and the additives had to be effective at temperatures which were above the decomposition points of the known additives, e.g., at temperatures which were generally within the range of 500 F. to 780 F. also found that when conventional additives were employed with functional fluids having higher thermal stability than that possessed by petroleum base stocks, the additives did not perform in a predictable manner, i.e., a material possessing antioxidant eflect or an extreme pressure-resisting eliect with the petroleum hydrocarbon lubricants generally did not possess such effects when used with the polyphenyl ether fluids.

Although the polyphenyl ethers possess extremely good thermal stability at temperatures of, say, over 550 F., they tend to deteriorate, not because of a decomposition reaction, but because at the higher temperatures they become quite readily oxidizable. The change in viscosity which is a consequence of the oxidation not only makes for inefficiency, but also may clog up the moving parts of the mechanism which the lubricant was originally intended to protect. Hence, when the polyphenyl ethers are to be used at the higher temperatures under conditions requiring exposure to air, it is necessary to inhibit oxidation phenomena which the higher temperatures favor.

Accordingly, an object of the present invention is the provision of improved polyphenyl ether fluid composi- It was 3,1?3373 Patented Mar. 16, 1965 tions. Another object of the invention is the provision of polyphenyl ether compositions having improved antioxidant properties. Amost important object of the invention is the provision of polyphenyl ether compositions which possess an improved resistance to oxidation at temperatures of over 550 F.

These and other objects hereinafter disclosed are provided by the invention wherein there is employed as antioxidant for the polyphenyl ether liquid fluids a compound of the formula where R is a benzenoid hydrocarbon radical which is free of olefinic and acctylenic unsaturation and contains from 6 to 12 carbon atoms, n is a number of from 1 to 2, m is a number of from 3 to 4, and the sum of m+n: is 5.

Compounds of the above formula include the bis(trihydrocarbonphosphinyl)iron tricarbonyls a )2 )a and the (trihydrocarbonphosphinyl iron tetracarbonyls R3P-F e (CO 4 Examples of the presently useful tricarbonyls are bis(triphenylphosphinyl)-, bis(tri-aor ,B-naphthylphosphinyl)-, bis(tribenzylphosphinyl)-, and bis(tri-4-tolylphosphinyl)- iron tricarbonyl. Illustrative of the presently useful tetracarbonyls are (triphenylphosphinyl)-, (trimesitylphosphinyl)-, [tris(2 phenylethyl)phosphinyl] [tris(4 biphenylyl phosphinyl [tris (tetrahydronaphthyl phosphinyl]-, or (diphenylbenzylphosphinyl)iron tetracarbonyl.

The presently useful bis(trihydrocarbonphosphinyl)- iron tricarbonyls and the (trihydrocarbonphosphinyl)iron tetracarbonyls are obtainable in known manner [see Cotton et al., J. Chem. Soc, 1440 (1960)] by the reaction of the stoichiometric amount of a trihydrocarbonphosphine with iron pentacarbonyl.

The polyphenyl ethers to which this invention pertains can be represented by the structure Kl fJ where n is a whole number from 2 to 5. The preferred polyphenyl ethers are those having all their ether linkages in the meta position since the all-meta linked ethers are the best suited for many applications because of their wide liquid range and high degree of thermal stability. However, mixtures of the polyphenyl ethers, i.e., either isomeric mixtures or mixtures of homologous ethers, can also be used to obtain certain properties, e.g., lower solidification points. Examples of the polyphenyl ethers contemplated are the bis(phenoxyphenyl)ethers, e.g., bis- (m-phenoxyphenyl)e-ther, the bis(phenoxyphenoxy)benzenes, e.g., mbis(m-phenoxyphenoxy)benzene, m-bis(pphenoxyphenoxy)benzene, o-bis(o-phenoxyphenoxy)ben zone, the bis(phenoxyphenoxyphenyl)ethers, e.g., bis[m- (m-phenoxyphenoxy)phenyl]ether, bis[p (p phenox phenoxy)phenyl]ether, rn- (m-phenoxyphenoxy) (o-phenoxyphenyl) ]ether and the his (phenoxyphenoxyphenoxy) tions, have been found to be particularly suitable as lubricants because such mixtures possess low solidification points and thus provide compositions having wider liquid ranges. Of the mixtures having only meta and para linkages, a preferred polyphenyl ether mixture of this invention is the mixture of S-ring polyphenyl ethers where the non-terminal phenylene rings are linked thorugh oxygen atoms in the meta and para position and composed, by weight, of about 65% m-bis(m-phenoxyphenoxy)benzene, 30% m-[(m-phenoxyphenoxy) (p-phenoxy phenoxy) ]benzene and 5% m-bis(p-phenoxyphenoxy)benzene. Such a mixture solidifies at about -l F., Whereas the three components solidify individually at temperatures above normal room temperatures.

The aforesaid polyphenyl ethers can be obtained by the Ullmann ether synthesis which broadly relates to ether forming reactions of, e.g., alkali metal phenoxides such as sodium and potassium phenoxides are reacted with aromatic halides such as bromobenzene in the presence of a copper catalyst such as metallic copper, copper hydroxides, or copper salts.

The bis(trihydrocarbonphosphinyl)iron tricarbonyls or the (trihydrocarbonphosphinyl)iron tetracaroonyls are combined with the fluid polyphenyl ethers to the extent of 0.01% to 2.0% and generally from 0.1% to 1.0%, by weight, depending upon the nature of the carbonyl compound and of the ether fluid. The present trior tetracarbonyls have an antioxidant effect on the polyphenyl ethers, generally. The concentration of the phosphinyliron carbonyl compound at which the desired antioxidant effect is obtained is readily determined by use of conventional testing procedures known to those skilled in the art. The effectiveness of the present additives may not be the same over the entire range of concentration; for example, while it has been noted that in most cases the abiilty of the agent with respect to anti-wear and extreme pressure lubrication improves markedly as the concentration is increased, the reverse may be true insofar as antioxidant etfect is concerned, lower amounts of the additive often resulting in a greater degree of stability to oxidation at the high temperatures than are attained by use of the greater amounts of the same additive.

The invention is further illustrated by, but not limited to, the following examples:

Example 1 The antioxidant effect of bis(triphenylphosphinyl)iron tricarbonyl was determined on a mixture of polyphenyl ethers consisting by weight of 65 m-bis (m-phenoxyphenoxy) benzene,

3 0 m-[ m-phenoxyphenoxy) p-phenoxyphenoxy) ]benzene,

5 m-bis (p-phenoxyphenoxy benzene.

The determination was conducted by bubbling air through 100 ml. samples of the mixture of ethers in the presence or absence of 5 percent by weight of the additive, employing an air flow rate of 5 liters per hour and conducting the test for 48 hours at 600 F. The viscosity of the treated samples was then determined at 100 F. The percent change in viscosity (before and after oxidation) was taken as an index of antioxidant activity. It was thus found that in the absence of an additive, the viscosity of the mixture of ethers increased 400% as a result of the treatment with air, whereas that which contained the 0.5% concentration of bis(triphenylphosphinyl)iron tricarbonyl increased only 28%.

Example 2 In this example, the antioxidant effect of bis(triphenylphosphinyl)iron tetracarbonyl was determined on the mixture of polyphenyl ethers described in Example 1 to which had been added uniform pieces of copper, steel and aluminum for the purpose of studying the effect of such metals on the efficiency of the carbonyl compounds. Us-

ing 20 ml. samples of the ether mixture containing 0.5% by weight of one said carbonyl compounds, air was bubbled into the samples, maintained at 600 F., for 24 hours at the rate of one liter per hour. Determination of the viscosities at 100 F. showed that the sample which contained bis(triphenylphosphinyl)iron tricarbonyl had undergone a viscosity increase of 19.2% as a result of the treatment and that which contained the (triphenylphosphinylfiron tetracarbonyl had undergone a viscosity increase of 27.7% as a result of the treatment. Both compounds are thus almost equally unaffected by the presence of metals when employed as antioxidant additives for the polyphenyl ethers.

The hydrocarbonphosphinyliron carbonyl compounds possess antioxidant effect for the polyphenyl ether functional fluids, generally. Thus, instead of the compounds shown above, similarly good results are obtained with bis(tri-2-, 3 or 4-tolylphosphinyl)iron tricarbonyl, bis (tricyclohexylphosphinyl)iron tricarbonyl, bis[tris(3- phenylpropyl)phosphinyl1iron tricarbonyl, bis[tris(2-, 3- or 4-butylphenyl)phosphinyl}iron tr'icarbonyl, (tri-a or ,8- naphthy1phosphinyl)iron tetracarbonyl, tris (2-, 3- or 4'- methylcyclopentyl)phosphinyliron tetracarbonyl, (tricumylphosphinyl)iron tetracarbonyl, [tris(biphenylyl)- phosphinyfliron tetracarbonyl, etc. Also, instead of the mixture of by weight of m-bis(m-phenoxyphenoxy)- benzene, 30% by weight of m-[(rn-phenoxyphenoxy) (pphenoxyphenoxy)]benzene and 5% by weight of m-bis- (p-phenoxyphenoxy)benzene which is used in the above examples, the polyphenyl ether component may be any one polyphenyl ether having from 4 to 7 benzene rings. For example, bis(triphenylphosphinyl)iron tricarbonyl or (triphenylphosphinyl)iron tetracarbonyl is a very good antioxidant for any one of the three ethers of the polyphenyl ether mixtures of the above examples, as well as for such other polyphenyl ethers as p-bis[p-(m-phenoxyphenoxy) phenoxy1benzene, or m[(m-phenoxyphenoxy)- (o-phenoxyphenoxy)]benzene, or m-bis[rn-bis[m-(pphenoxyphenoxy)phenoxy]benzene, or mixtures thereof in any proportion. Lubricant mixtures of ethers are generally soconstituted as to give simultaneously an optimum of thermal stability and lubricity at the tempera tures to which they will be exposed in operation.

Since the quantity of the phosphinyliron carbonyl compound which is employed with the polyphenyl ether fluid will vary with the nature of the polyphenyl ether and the nature of said carbonyl compound, it is evident that no rigid limits of antioxidant content can be set forth. Generally, polyphenyl ether compositions comprising from 0.01% to 1.0% by weight of the present additive demonstrate antioxidant effect. Determination of the optimum quantities is readily conducted by routine procedures, as will be apparent to those skilled in the art. Hence, the amount of the carbonyl compound to be used can best be expressed simply as an antioxidant amount. Variations or modifications of the compounds and quantities employed in the examples can be made to accommodate different requirements, so long as the additive belongs to the hydrocarbonphosphinyliron carbonyl compounds herein shown, and the polyphenyl ether fluid consists of polyphenyl ethers having from 4 to 7 benzene rings.

The present phosphinyliron tri-or tetracarbonyls may be used in the polyphenyl ether fluids with other additives, e.g., pour point depressants, viscosity index improvers, crystallization suppressants, dyes, etc.

Other modes of applying the principles of this invention may be employed instead of those specifically set forth above, changes being made as regards the details herein disclosed, provided the elements set forth in any of the following claims, or equivalents thereof may be employed.

What we claim is:

1. A functional fluid composition consisting essentially of a polyphenyl ether having from 4 to 7 benzene rings and from 3 to 6 oxygen atoms and from 0.01% to 1.0%

5 by weight of the composition of the compound of the formula (R P),,Fe(CO) wherein R is a benzenoid hydrocarbon radical which is free of olefinic and acetylenic unsaturation and contains from 6 to 12 carbon atoms, n is a number of from 1 to 2, m is a number of from 3 to 4, and the sum of m+n is 5.

2. A functional fluid composition consisting essentially of a polyphenyl ether having from 4 to 7 benzene rings and from 3 to 6 oxygen atoms and from 0.01% to 1.0% by weight of the composition of bis(trihydrocarbonphosphinyl)iron triearbonyl wherein the hydrocarbon radical is benzenoid, is free of olefinic and acetylenic unsaturation and contains from 6 to 12 carbon atoms.

3. A functional fluid composition consisting essentially of a polyphenyl ether having from 4 to 7 benzene rings and from 3 to 6 oxygen atoms and from 0.01% to 1.0% by weight of the composition of (trihydrocarbonphosphiny1)iron tetracarbonyl wherein the hydrocarbon radical is benzenoid, is free of olefinic and acetylenic unsaturation and contains from 6 to 12 carbon atoms.

4. A functional fluid composition consisting essentially of a mixture of metaand para-polyphenyl ethers having from 4 to 7 benzene rings and from 3 to 6 oxygen atoms and bis(triphenylphosphinyl)iron tricarbonyl in an amount which is from 0.1% to 1.0% by weight of the composition.

6 5. A functional fluid composition consisting essentially of a mixture of metaand para-polyphenyl ethers having from 4 to 7 benzene rings and from 3 to 6 oxygen atoms and (triphenylphosphinyl)iron tetracarbonyl in an amount which is from 0.01% to 1.0% by Weight of the composition.

References Cited in the file of this patent UNITED STATES PATENTS 3,034,700 Hickman May 15, 1962 FOREIGN PATENTS 851,651 Great Britain Oct. 19, 1960 OTHER REFERENCES 

1. A FUNCTIONAL FLUID COMPOSITION CONSISTING ESSENTIALLLY OF A POLYPHENYL ETHER HAVING FROM 4 TO 7 BENZENE RINGS AND FROM 3 TO 6 OXYGEN ATOMS AND FROM 0.01% TO 1.0% BY WEIGHT OF THE COMPOSITION OF THE COMPOUND OF THE FORMULA (R3P)NFE(CO)M WHEREIN R IS A BENZENOID HYDROCARBON RADICAL WHICH IS FREE OF OLEFINIC AND ACETYLENIC UNSATURATION AND CONTAINS FROM 6 TO 12 CRBON ATOMS, N IS A NUMBER OF FROM 1 TO 2, M IS A NUMBER OF FROM 3 TO 4, AND THE SUM OF M+N IS
 5. 4. A FUNCTIONAL FLUID COMPOSITON CONSISTING ESSENTAILLY OF A MIXTURE OF META- AND PARA-POLYPHENYL ETHERS HAVING FROM 4 TO 7 BENZENE RINGS AND FROM 3 TO 6 OXYGEN ATOMS AND BIS(TRIPHENYLPHOSPHINYL)IRON TRICARBONYL IN AN AMOUNT WHICH IS FROM 0.1% TO 1.0% BY WEIGHT OF THE COMPOSITION. 